Rotary injectors were used to treat molten aluminum, such as disclosed in U.S. Pat. No. 6,589,313 for instance. In these applications, a rotary injector, known as a rotary flux injector, was used to introduce salts into molten aluminum held in a large volume furnace.
An example of a known rotary flux injector is shown in FIG. 1 as having a rotary shaft 15, typically made of a temperature resistant material such as graphite, leading to an impeller mounted to the end thereof. A supply conduit is provided within the rotary injector, extending along the shaft and leading to an axial outlet across the impeller. A fluxing agent, typically in the form of a mixture of particulate salts, is entrained along the supply conduit by a carrier gas. The impeller has a disc shape with blades or the like to favour the mixing of the fluxing agent in the molten metal, in an action referred to as shearing.
Known rotary flux injectors were satisfactory to a certain degree. Nonetheless, because the fluxing time limited the productivity of furnaces, it remained desirable to improve the shearing efficiency, with the objective of reducing fluxing time and improving productivity. Moreover, the efficiency of rotary flux injectors was limited by occurrences of blockage of the supply conduit which was known to occur especially at lower molten aluminum temperatures (e.g. below 705-720° C.). Henceforth, rotary flux injectors were not used until the molten aluminum reached a certain temperature threshold, and this heating period was thus not productive from the standpoint of fluxing.